Inverter simply means it is a variable speed compressor designed to ramp up or down depending on the load conditions. In your case if you open the room and add a load beyond its capacity it will not keep up. So it will ramp up to full capacity and stay there. This is not damaging to the unit because it is designed to run as needed. You just won’t get the energy savings they provide by reducing the power when the temperature comes down.It will just run continuously. While it will not cool a larger area well (more than 600 sq. ft., it’s approximate load capacity), it will do a good job of drying the air. Humidity is the bigger problem in areas where summer humidity is high. So by running continuously it will remove the moisture and you will be more comfortable at a higher temperature. So even though it won’t drop the temperature much in the larger area. It will make you far more comfortable. But watch for icing, sometimes if conditions are right it will ice up from all the moisture. You can tell this is happening when the water stops dripping from the unit. If this happens turn off the cooling, let it run in fan mode until it thaws. But the unit will suffer no damage from continuous use. But like anything else it has a life expectancy. It will wear out eventually.